新增权限 query_all_instances

[LeoQuote]

拥有该权限的用户可以查询所有的数据库实例

相关issue #154

[codecov]

Codecov Report

Merging #199 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #199      +/-   ##
==========================================
+ Coverage   73.12%   73.14%   +0.01%     
==========================================
  Files          63       63              
  Lines        6974     6979       +5     
==========================================
+ Hits         5100     5105       +5     
  Misses       1874     1874

Impacted Files	Coverage Δ
sql/models.py	94.6% <ø> (ø)	⬆️
sql/query_privileges.py	58.14% <100%> (ø)	⬆️
sql/utils/resource_group.py	73.07% <100%> (ø)	⬆️
sql/tests.py	100% <100%> (ø)	⬆️

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[hhyo]

我的印象中代码和model的code不一致貌似会判断有误